French Patent # 669,030 - Simplex

This is the earliest Simplex patent that I have been able to uncover. It shows a single pulley wheel, pull-chain, derailleur that I believe was marketed under the name ‘Le Simplex’. The derailleur mounts onto the wheel axle, and the oval slot in the mounting bracket allows some ability to tune the chain gap to suit the freewheel. Frank Berto discusses a 1928 Simplex design - and I think that this is it.